Currently, a gateway device called an IP Multimedia Subsystem (IMS) Gateway (IG) is known. The IG contains the necessary IMS subscription information (e.g., an IMS Subscriber Identity Module (ISIM) containing an IMS Private User Identity (IMPI) and one or more IMS Public User Identities (IMPUs)) to access an IMS network. The IG also works as a residential gateway to connect a local area network (LAN) to a wide area network (WAN) such as the Internet. A basic configuration of an IG is proposed in, for example, WO 2006/045706.
In the near future, it will be common that a single user or a party (e.g., a company) possesses a plurality of IGs, each of which involves a separate LAN. For example, a user may have the first IG in his/her house and forms the first LAN including the first IG and home devices such as a desktop computer. The user may also have the second IG in his/her car and forms the second LAN including the second IG and mobile devices such as a notebook computer.
In this situation, it is desirable to treat these two LANs as a single personal network (PN). The Converged Personal Network Server (CPNS) proposed by the Open Mobile Alliance (OMA) partly addresses this desire (for details regarding the CPNS, see OMA CPNS WID proposal slides, August 2008). According to the mechanism proposed by the OMA, each IG gathers information regarding its LAN and publishes the information to the CPNS. It is thereby possible for the user to know, through the CPNS, the information (LAN information) about the first and second LANs that form the PN.
However, this mechanism does not work in the desired manner if the first and second IGs belong to different IMS networks (which may be operated by different IMS operators). In this case, the first IG publishes its LAN information to the first CPNS located in the first IMS network, while the second IG publishes its LAN information to the second CPNS located in the second network. However, there is no mechanism to associate the LAN information managed by the first and second CPNSs with each other.
Accordingly, it is either quite difficult or impossible for a device (either in the first or second LAN or external to them) to recognize that the first and second LANs form a single PN and collect the information regarding the PN. In other words, in the conventional art, if respective LANs that should be included in a PN belong to different IMS networks, it is either quite difficult or impossible to make them form a single group in a recognizable manner. If a plurality of LANs are not recognized as a single group, it is not easy for them to cooperate with each other.